By way of background, a driveline angle (also known as the working angle) refers to the difference of the component angles on the drive side and driven side of a U-joint. All angle measurements are taken with zero degrees being parallel to the ground. As shown in FIGS. 1a and 1b, each component on either side of the U-joint will rotate at the same rotational speed when the difference of the component angles on the drive side and driven side of the U-joint is zero. As shown in FIGS. 2a and 2b, if the difference of the component angles is not zero, then the U-joint will cause the component on the driven side of the U-joint to rotate at a changing rate when the U-joint is rotated.
As shown in FIG. 3, the speed of the component on the driven side of the U-joint will increase and decrease twice each 360 degree rotation. The constantly changing acceleration is commonly known as torsional acceleration and is measured in radians per second squared (rad/sec*2), where 1 radian is equal to 57 degrees. Torsional accelerations caused by the effect of U-joints are referred to as 2nd order torsionals (twice per rotation of the driveshaft). The effect of U-joint torsional acceleration can be cancelled for each driveshaft by ensuring that the working angles of the U-joints at each end of the driveshaft both have the same working angle.
In addition to torsional acceleration, an inertial component is generated and is commonly known as driveline inertia, which is measured in foot pounds (ft-lbs). Typically, there are two overall system inertia values, drive and coast. Drive inertia occurs when power is being supplied by the engine through the transmission to the drive train. Coast inertia occurs when the vehicle is coasting and power is being supplied by the inertia of the vehicle and passing back through the axles to the rest of the drive train. Unlike U-joint torsional acceleration, the effect of driveline inertia cannot be cancelled by ensuring that the working angles of the U-joints at each end of the driveshaft both have the same working angle. However, the driveline inertia can be reduced by reducing component working angles and/or by using lower inertia driveline components.
An improperly set driveline angle can cause high driveline inertia and torsional acceleration. In general, the greater the working angles, the greater the potential for high driveline inertia and torsional acceleration. An improperly set driveline angle can result in increased vibration, noise, and a reduction of the life of the driveline. For example, the vehicle can exhibit growling during acceleration or deceleration. Typically, the growl is caused from the gearing going through backlash at low torque or float conditions and is more prevalent during deceleration or lightly loaded torque conditions.
In addition, an improperly set driveline angle can cause decreased durability or potential failure of driveline components. For example, the transmission may fail due to synchronizer pin breakage, synchronizer ring breakage, auxiliary drive gear and mainshaft spline wear, and auxiliary drive gear and range sliding clutch teeth fretting. The axle may fail in the vicinity of the power divider. Also, increased wear may occur to the carrier bearings, the slip spline and fretting may occur to the U-joint. Thus, it is desirable to provide an user-friendly tool for diagnosing and correcting problems associated with improperly set driveline angles.